The endocannabinoid system (ECS) is a lipid signaling system comprising endocannabinoids (ECs), which are lipids derived from arachidonic acid, the G-protein-coupled cannabinoid receptors CB1 and CB2, as well as several other actual and potential physiological targets involved in the synthesis, transport and degradation of ECs. The major ECs are 2-arachidonoylglycerol (2-AG) and N-arachidonoyl ethanolamide (AEA; anandamide) which modulate synaptic transmission by retrograde signaling via CB1 receptors and exert potent immunomodulatory effects via both CB1 and CB2 receptors. The ECS has been implicated in physiological and pathophysiological conditions including inflammation, pain, psychiatric disorders and metabolic reprogramming. The ECS provides a primary on-demand protection system against acute excitotoxicity in the central nervous system (CNS) (Marsicano et al., 2003, Science, 302, 84-8.)
Therapeutic strategies within the ECS include the use of cannabinoid receptor agonists and antagonists, blockage of hydrolytic enzymes degrading ECs, such as fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), as well as inhibition of EC cell membrane trafficking. Although so far no membrane protein for EC transport has been identified, several lines of evidence suggest a facilitated membrane transport involving both membrane and cytoplasmic targets (Chicca et al., 2012, J Biol Chem. 287, 36944-67; Fowler C J., 2013, FEBS J., 280:1895-904). The movement of AEA across the cell is affected by the concentration gradient enhanced by rapid intracellular hydrolysis of AEA catalyzed by FAAH. Therefore, FAAH plays a key role in AEA cellular uptake by generating an inward concentration gradient for AEA, which is the major driving force for its cellular uptake.
Using the commercially available AEA uptake inhibitors UCM707, OMDM-2 and LY2183240 evidence for bidirectional transport of both AEA and 2-AG across cell membranes, as well as a common mechanism of cellular membrane transport for all arachidonate-based ECs was recently provided (Chicca et al., 2012, J Biol Chem. 287, 36944-67). Since all of the available inhibitors are only moderately potent and show low selectivity towards AEA transport inhibition over FAAH inhibition or other cytoplasmic targets, investigations of the mechanisms of AEA and 2-AG cellular uptake are hampered by a lack of adequate tools. As indicated by a recent study (Nicolussi et al., Pharmacol Res., 2014, 80:52-65), the CNS pharmacology of inhibitors of endocannabinoid breakdown and inhibitors of endocannabinoid membrane transport is distinctly different and that inhibition of FAAH and AEA cellular uptake, respectively, can be independent from each other. Prior art has shown the use of Dodeca-2E,4E-diene amides as specific AEA cellular uptake inhibitors as anti-inflammatory agents in skin (WO 2010136221 A1). The potential therapeutic value of specific AEA cellular uptake inhibitors to treat CNS related diseases remains largely unknown. In a murine model of multiple sclerosis, the AEA cell membrane transport and FAAH inhibitor UCM707 showed beneficial effects by reducing microglial activation (Ortega-Gutierrez et al., 2005, FASEB J., 19, 1338-40). Using UCM707, it was shown that an increased AEA tone limits excitotoxicity in vitro and in a model of multiple sclerosis (Loria et al., 2010, Neurobiol Dis., 37, 166-76). The non-specific AEA cellular uptake and FAAH inhibitor AM404 was shown to reduce the rewarding effects of nicotine and nicotine-induced dopamine elevations in the nucleus accumbens shell in rats (Sherma et al., Br J Pharmacol., 2012, 165, 2539-48). The non-specific AEA cell membrane transport inhibitor VDM-11 was shown to modulate sleep and c-Fos expression in the rat brain (Murillo-Rodríguez et al., Neuroscience, 2008, 157, 1-11). The administration of AEA cell membrane transport inhibitors OMDM-2 or VDM-11 was shown to promote sleep and decreases extracellular levels of dopamine in rats (Murillo-Rodríguez et al., Physiol Behav. 2013, 109, 88-95). UCM707 was shown to behave as a symptom control agent in models of Huntington's disease and multiple sclerosis, but failed to delay/arrest the progression of different motor-related disorders (de Lago et al., Eur Neuropsychopharmacol., 2006, 16, 7-18). As shown by a study using UCM707 and AM404, AEA transport inhibitors may have potential in the treatment of painful diabetic neuropathy (Hasanein and Soltani, 2009, Clin Exp Pharmacol Physiol. 36, 1127-31). Targeting fatty acid binding protein (FABP) intracellular AEA carriers has recently been suggested to be a strategy to generate anti-inflammatory and anti-nociceptive drugs (Berger et al., 2012, PLoS One., 7(12):e50968). However, the pharmacology between the inhibition of AEA cell membrane transport and the inhibition of cytoplasmic carriers is expected to be different, as exemplified by the fact that FABP5 inhibitors do apparently not show the same degree of cannabimimetic effects observed with the potent AEA cell membrane transport inhibitor guineensine (Kaczocha et al., PLoS One. 2014, 9(4):e94200; Nicolussi et al., 2014, Pharmacol Res., 80, 52-65).
Overall, there is a need for novel inhibitors of AEA cell membrane transport with superior specificity and potency to address CNS and inflammation related diseases involving aberrant endocannabinoid tone or in which AEA cellular uptake inhibition can target pathophysiological conditions. Given the fact that AEA and other endocannabinoids are involved in both synaptic processes via retrograde signaling and immunomodulatory processes, specific inhibitors of AEA cell membrane transport are expected to exert therapeutic effects in neuropsychiatric diseases involving neuroinflammation. When the degradation of AEA and other endocannabinoids is blocked, for example by covalent inhibition of FAAH, the resulting intracellular accumulation of AEA (Chicca et al., 2012, J Biol Chem., 287, 36944-67) is expected to potentially also have proinflammatory effects via oxygenation of AEA and possibly other endocannabinoids by cyclooxygenase-2 (discussed in Chicca et al, 2014, ACS Chem Biol, http://pubs.acs.org/doi/abs/10.1021/cb500177c). Therefore, the inhibition of degradation of AEA and the inhibition of cell membrane transport are distinct pharmacological interventions. Moreover, specific inhibition of AEA cell membrane transport, unlike inhibition of FAAH or cytoplasmic carriers, is expected to differentially modulate the AEA tone without leading to activation of TRPV1 channels via intracellular AEA accumulation.
Our attention, therefore, is focused on the identification of new class of molecules able to specifically inhibit AEA cellular uptake that do not affect hydrolytic enzymes, such as the serine hydrolase FAAH. We show that these compounds trigger cannabimimetic behavioral effects and inhibit inflammation, in particular neuroinflammation.
The present invention relates to thiazolidinone derivatives and their use for the treatment of psychiatric or neurological disorders and inflammation, in particular neuroinflammation. The use of the compounds of the invention in a method for treatment of psychiatric or neurological disorders is related to attenuation of neuroinflammation and neuronal retrograde signaling mediated via AEA and other endocannabinoids. In example, such diseases include multiple sclerosis, epilepsy, Alzheimers disease, bipolar diseases, schizophrenia, sleeping disorders, and spinal cord injury (Ashton and Moore, Acta Psychiatr Scand. 2011, 124, 250-61; Aso and Ferrer I, Front Pharmacol., 2014, 5, 37; Correa et al. Vitam Horm. 2009, 81, 207-30; Hofmann and Frazier, Exp Neurol. 2013, 244, 43-50; Pacher et al., Pharmacol Rev., 2006, 58, 389-462).